Out-of-round grinding – the highest precision for non-circular geometries

Out-of-round grinding of cams, camshafts, cam elements and pump rings using CBN grinding wheels

Camshafts are the perfect examples to show that the machining of non-circular workpieces is an essential part of the production process. Cylindrical grinding was developed to achieve a perfectly round shape. Out-of-round grinding, however, gives the workpiece a defined non-circular shape, with the grinding process perfecting the final surface quality.

Examples of non-circular shaft-type components include camshafts, cam discs and pump shafts. The various manufacturing tasks provided to us by our customers also require different demands on the machine concept. Even the execution of a closely defined machining task – such as the grinding of camshafts for passenger cars – illustrates that today’s market demands cannot be met with one single machine concept. A modular machine concept is therefore essential for out-of-round machining. This may involve using multiple grinding spindles for pre-grinding and finishing or for the complete machining of the component. It may also require a machine with two slides for simultaneous grinding, or synchronous support grinding.
 

CBN grinding technology for out-of-round machining

The use of CBN grinding technology is high-tech for out-of-round grinding. In the future, productivity rates will continue to increase with a demand on cutting speed also required. For less stable components with slight grinding allowances, such as composite camshafts, there is a need to develop grinding systems that generate noticeably lower grinding forces. Increasing and constantly changing market demands will continue to drive innovations in out-of-round grinding technology.
In order to meet the diverse demands made on grinding machines and machining processes, EMAG offers a wide range of technology modules and machines that adapt in the best possible way to any production environment (see below).
 

Sample applications

Camshaft machining is a typical example of out-of-round grinding. In an implemented turnkey project, four twin-cams are ground with manual loading. The challenge of this application is roughing a machining allowance of up to 3 mm and finishing the cams with just a single grinding wheel. These conflicting demands were met with a vitrified bonded CBN grinding wheel.

Another example is the complete-machining of camshafts for commercial vehicles: Twelve control cams, six pump dogs, seven bearing surfaces, the thrust bearing and the ends with their tapers and shoulders are ground in a single clamping  operation. As the grinding of hardened shafts often releases internal stresses, and cam grinding has an influence on the concentricity of the bearing surfaces, the components cannot be machined  in a single pass. The best way to achieve the required quality is to machine the shaft in a single clamping operation.